Asphalt (and other surface pavement materials such as macadam and tarmac) covers many surfaces such as roadways, runways and parking lots. Over time, wear and tear from vehicle traffic, weather, and oxidation, occurs and leads to cracks, bumps, dips, ruts and other irregularities in the asphalt. These unwanted formations are both an eyesore and a safety hazard that is dangerous to traffic.
There are a number of ways to refinish asphalt surfaces and to remove the unwanted irregularities. For example, a common method for repairing damaged asphalt includes removing the damaged asphalt from a surface and replacing it with new asphalt. The old asphalt is discarded and new asphalt material is used to refinish the surface. While this method is effective in renewing damaged asphalt surfaces, it is neither cost efficient nor environmentally friendly.
To address environmental and cost issues, systems have been developed that recycle at least a portion of the removed asphalt and reapply it to the refinished surface. These systems reduce material costs, eliminate waste and dumping costs, and are more environmentally conscious. These systems, however, do not effectively break up, remove, and reuse all existing asphalt and still typically requires the use of new asphalt.
One method of recycling and reapplying asphalt is Hot In-Place Recycling (“HIR”). Unlike cold recycling methods, HIR involves a first step of heating the damaged asphalt to soften the upper layer to a predetermined depth. Exemplary methods of heating asphalt are disclosed in U.S. Pat. No. 3,970,404. The heated layer of damaged asphalt is then removed through a scarification process. Commonly, between one and two inches of the top layer is removed during scarification. The removed asphalt is fed to a mixer that sifts out large, unusable pieces of asphalt, leaving only small, workable pieces. New material or reconditioning agents may be added to the reclaimed asphalt during the mixing process. The combination of old material and new additives is heated to enhance blending. The new mixture is then reapplied to the surface and compacted and smoothed by a steamroller while the surface is still hot.
HIR is an effective method for recycling damaged asphalt. However, several limitations exist in traditional HIR methods. One drawback is that multiple separate machines are traditionally required to perform the HIR process, including heating machines, scarifying machines, repaving machines and smoothing machines. The multiple machines increase both time and cost of repaving jobs. Another drawback is that the process of recycling and repaving asphalt is very slow, often moving at speeds of less than 10 feet per minute. Further, HIR is an inferior system for removing and reclaiming the damaged asphalt and requires more additives for the recycled asphalt. Thus, a need exists for an improved method and system for recycling and reapplying asphalt.